CNN says that "Frank, a 16-term Democrat, will announce Monday he does not intend to seek re-election in 2012, according to a statement from [his] office."

Back in February, Frank announced he would run again in 2012, saying he wanted to "defend the Wall Street Reform and Consumer Protection Act" that he helped enact and wanted to work to "reduce significantly America's swollen, unnecessary, worldwide military footprint." It isn't known yet why he's apparently reversed course.